1. Field of the Invention
This invention relates to a horizontal multiplaten press which is used for pressing sheet materials under heat for manufacturing plywood, decorative laminate or veneer and which has a plurality of horizontally movable vertical heating platens which are equally spaced apart from one another so that a sheet material may be heated and pressed between every two adjoining heating platens.
2. Description of the Related Art
There is known a multiplaten press which is mainly used for manufacturing plywood. It usually comprises an upper frame, a lower frame, a plurality of heating platens which are horizontally disposed between the upper and lower frames and a moving platen which is vertically movable by a ram cylinder provided on the lower frame. After the sheet materials to be pressed have each been placed between every two adjoining heating platens, the moving platen is raised to push up the heating platens one after another, beginning with the lowermost one, whereby the press is closed for pressing the sheet materials under heat for a predetermined length of time.
Each heating platen is provided with a supporting lug at each of the four corners thereof and each lug is supported on a structure which is supported on a prop and shaped like a ladder, whereby each heating platen is supported in its horizontal position. Each heating platen has a thickness which is greater than what is required for providing the strength as required for supporting the sheet material to be pressed, since a high degree of rigidity is additionally required for preventing the platen from bending due to its own weight. The platen has, therefore, a heavy weight.
As the heating platens are heavy, there arises a large difference between the pressure which is applied to the upper sheet material and the pressure to the lower sheet material. This difference brings about the lack of adhesion uniformity in each sheet material and a reduction of its thickness. Moreover, the ram cylinder for raising or lowering the heating platens must have a large diameter and a large amount of a working fluid must be supplied to the cylinder. Therefore, a large fluid pressure unit is required and increases the size of the press per se.